Steering gear for variable track vehicles



1949- E. T. J. TAPP ET AL 2,480,309

' STEERING GEAR FOR VARIABLE TRACK VEHICLES FiledJuly 31, 1947 Y 1 2 Sheets-Sheet 1 m fizayai wk Aug. 30, 1949. E. T. J. TAPP ETAL 2,480,309

STEERING GEAR FOR VARIABLE TRACK VEHICLES Filed July 31, 1947 2 Sheets-Sheet 2 Patented Aug. 30, 1949 STEERING one son VARIABLE relies VEHICLES I a 1 Ernest T. J. Tapp and Joseph Davey; Flet,:Eng-' land, assignors. toPest Control Limited, Harston; Cambridgeshire, England,a British com- Application duly'31, unseen- 151 465694 In'Grat Britain May 23,1946 Section 1, PublioLaw 69 0, August}, Pate'n't expires May 23, I966 claims. '1

' This invention relates to an improved steer ing gear for variabletrac'k vehicles.

It may often be desirable for special purposes to vary the track of a vehicle. For example with agricultural vehicles employed for spraying or cultivating rows of crops it is desirable'to' be able to widen or narrow the track at will to suit the width of crop rows, so that the Wheels of the vehicle always run along the space between adjacent rows. In'vehicles tifthis type which are provided with th'e conventional Ackermann steering, it is neces's'ary'to' adjust the length of the trackrod each time the track of the steered wheels is varied. v

According to this invention there is provided an improved steering gear for variable track vehicles comprising a pivotal riiouhtingfor each steered wheel and its associated steering arm, said mounting being displaceable transversely of the vehicle, a radiusrod connectedtosaicl pivotal mounting and extending longitudinally of the vehicle, and a connecting rod operatively connected at one endtofsa id' steering arm and at the-other end to steering control means in such 7 a way as to remain parallel in plan to said radius rod on transverse displacement of said pivotal mounting.

The improved steeririg gear makes it possible to displace the steered wheels transversely of the vehicle to widen or narrow th'etr'ack, Without any consequential adjustment of the steering mechanism being necessary, and without substantial alteration in the direction in which the wheels lie.

Steering motion*may be transmitted from a control lever linked by the conne'cting rod. to the steering arm, the controll ever being pivotedin a bearing to whichthe' end" of the radius rod is connected, so' that thesteering' arm and control lever, and the radius rod; and connecting rod, respectively form opposite pairs of sides of a parallelogram" asseenin plan; The control lever for one wheel is linked to 'the control lever for the other wheel and to a steering box in known manner.

Preferably the pivotal wheel mounting is arranged for rectilinear transverse displacement, and the control lever bearing is permitted a limited longitudinal movement but is restrained from transverse movement, but it is also possible to employ a, fixed control lever bearing and to arrange the pivotal wheel mounting for transverse displacement along an are centered on the bearmg.

It is preferable, particularly when the vehicle is to nave the agriculturalma'ch v y Y in forks. The front h 'lsm y d on t b ax es, a

A rererreq efiincd or thefinventidn will now be described by wa ence'to' the acco'mpalri g dr wings, Figs: 1 and 2 of which show i e-unt y a plan and aside elevation of the to of ai vehicle chassis. Fig. 3 is a vertical seetianawiew; on a somewhat enlarged scale, of .thelpivotal mounting for the e e efl. v ,7 f

Referring no v trie'dr wings'tne' rqht'wheels l of the vehicle are mounted on v clamped spring forks 12. The I v the forks are supported by upper lower I bearing's 4 v anus, slidabl earned on tra sverse nor-1+ zontal tubular'm er 6 and" i, Tail" pieces}; engagei'ngui u din aiithi'rdtransver e horizontal tubular in mberi 9. Locatiori'bojlt's', not shown, areiprovided jorlocking the slidabl'e bearings at'variouspositions'oh; the tra verse members. Steering arm's lfandlz'ar o rotate 0 example with refer- The'twobell cranks f8, I 9are'pivotallymo inted in' bearings carrie sprin blades 25; 25 secured to the side; members of thef chassi'sf so as to enn a 'nievnint rthe bearings tangen 1a v gnu inal di'i'eeti'onof the frame. Ea'ch' belrcrarikifieann is attached toone end of a radius roa'f f, zfs, t e other nd or which is rotating seemed" arsenathe" head bearingof the r espec ive' s rig fprk Each connecting rod l3} l4 andraditi's 27,28 forms a parallelogram-asgseen invplan-with its, respec- 7 a mean track width, i. e. half-Way between their greatest width as shown in full lines in Fig. 1, and their least width as shown in dotted lines. A normal steering box 29 and drop arm 36 may be employed to actuate the steering by means "ed to 3 of a link 3| extending from the drop arm 30 to the arm I! of the bell crank IS.

The pivotal mountings for the steerable wheels are illustrated in Fig. 3 which shows a section through the fork, stem and mountings for one of the front wheels. Thus one of the steering arms II is secured to a vertical rod 32. This cooperates with a tube 33 containing a coil spring 34 which is guided in an upper tube 35 by the lower fixed bushing 36, there also being an upper sliding bushing 31 attached to the lower tube. A smaller tube 38 is also fixed to the fork and forms a guide for the plunger 39 attached to the splined steering shaft 32 from which it receives its steering movement through the splined collar 40 which caps the tube 38. The latter also forms a cavity for oil which in conjunction with the action of the piston and holes in the tube wall serves hydraulically to damp the movement of the spring 34. The shaft 32 is not permitted vertical movement relative to the vehicle frame and carries the steering arm I l at its upper end. The outer tube 35 is fixed to the vehicle frame by cylindrically bored brackets 4 and through the medium of the tubular cross members 6 and l, as already explained.

This particular method of mounting is subject to considerable variation, and the detailed description is given merely for greater clarity in the understanding of the general principles of the invention, as already described hereinabove.

An alternative means for transmitting steering motion to the steered wheels may comprise a transverse shaft rotatably mounted in a bearing at each side of the vehicle, each bearing being slideable fore and aft and being connected by a radius rod to the head bearing of the wheel on its respective side. Two control levers are carried on the shaft, each lever being linked by a connecting rod to its respective steering arm and each being so disposed on the shaft that its associated connecting rod is parallel in plan to its respective radius rod.

We claim:

1. An improved steering. gear for the steered wheels of a variable track vehicle, comprising a pivotal mounting for each steered wheel, said mounting being displaceable transversely of said vehicle, a steering arm associated with each said steered wheel, a radius rod connected to each said pivotal mounting and extending longitudinally of said vehicle, and a connecting rod operatively connected at one end to said steering arm and at the other end to steering control means in such a way as to remain parallel in plan to said radius rod on transverse displacement of said pivotal mounting.

2. An improved steering gear for the steered wheels of a variable track vehicle, comprising a pivotal mounting for each steered wheel, said mounting being displaceable transversely of said vehicle, a steering arm associated with each said steered wheel, a steering control lever pivoted about an axis, a radius rod pivoted at one end about the axis of said pivotal mounting and pivoted at the other end about the axis of said steering control lever, and a connecting rod linking said steering arm to said steering control lever, said steering arm and said steering control lever, and said radius rod and said connecting rod, respectively forming opposite pairs of sides of a parallelogram when viewed in plan.

3. An improved steering gear for the steered wheels of a variable track vehicle, comprising a head bearing for each steered wheel, said head bearing being slidably mounted on a cross-member of said vehicle, a steering arm associated with each said steered wheel, a steering control lever pivoted about an axis displaceable foreand-aft with respect to said vehicle, a radius rod pivoted at one end about the axis of said head bearing and pivoted at the other end about the axis of said steering control lever, and a connecting rod linking said steering arm to said steering control lever, said steering arm and said steering control lever. and said radius rod and said connecting rod, respectively forming opposite pairs of sides of a parallelogram when viewed in.

plan.

4. An improved steering gear for the two steered wheels of a variable track vehicle, comprising a head bearing at each side of said vehiclefor each steered wheel, said head bearings being slideably mounted on a cross-member of said vehicle, a steering arm associated with each said steered wheel, a bell crank lever operatively connected to each steered wheel, each bell crank lever being pivoted about an axis displaceable fore-and-aft with respect to said vehicle, a rod linking together one arm of each said bell crank lever, the second arm of each lever forming the steering control arm of its respective steered. wheel, a radius rod at each side of said vehicle pivoted at one end about the axis of said head bearing and pivoted at the other end about the axis of said bell crank lever, and a connecting. rod at each side of said vehicle linking said steer-- ing control arm to its respective steering arm, said steering arm and said steering control arm, and said radius rod and said connecting rod, respectively forming opposite pairs of sides of a parallelogram.

5. An improved steering gear for the two steered wheels of a variable track vehicle, comprising a head bearing at each side of said vehicle for each steered wheel, said head bearings being slideably mounted on a cross member of said vehicle, a steering arm associated with each said steered wheel, a transverse steering control shaft rotatably mounted in a bearing at each side of said vehicle, each said control shaft bearing being slideable fore-and-aft and being connected by a radius rod to the head bearing of the wheel on its respective side, two control levers carried on said shaft, each lever being linked by a connecting rod to its respective steering arm and being so disposed on said shaft that its said associated connecting rod is parallel in plan to its said respective radius rod.

ERNEST T. J. TAPP.

J. DAVEY.

No references cited. 

